使用WMI改变显示器亮度

前言

最近遇到了新的需求，需要通过代码去改变显示器的亮度。通过调研发现，改变显示器亮度的方式有三种
1.调节伽马值
2.使用WMI
3.使用DDC/CI协议
然而这三个方法都各有缺点：
第一个方式：调节伽马值，效果会收到显示器的影响，有的显示器，或者驱动，会去校准显示器亮度。如果你改变了伽马值，在你的鼠标脱离程序的时候，屏幕亮度就会被校准回去。
第二个方式：使用WMI。使用WMI是不支持台式电脑的，只能在笔记本上面生效。这个也是我在调试的时候发现的，总是被拒绝访问，去查了才知道台式不支持。然后在笔记本下做了校验，发现确实是可以实现的。
第三个方式：使用DDC/CI协议。DDC/CI，全称为 Display Data Channel / Command Interface，是一种用于计算机显示设备（如显示器、投影仪等）之间通信的协议。它允许计算机与显示器共享信息，使得计算机能够读取显示器的状态和特性，例如分辨率、色彩特性等。

DDC/CI 的构成
DDC/CI 协议主要构建在两个较早的标准之上：

DDC (Display Data Channel):

DDC 是一种用于监视器和计算机之间通信的协议，允许计算机访问显示器的 EDID（Extended Display Identification Data）信息，EDID 是描述显示器特性的标准化数据结构。
CI (Command Interface):

Command Interface 允许计算机向显示器发送命令，包括但不限于调节明亮度、对比度、开启或关闭显示器等功能。

DDC/CI 的工作原理
I²C 通信: DDC/CI 的底层协议使用 I²C（Inter-Integrated Circuit）总线，使其可以支持主设备和从设备的双向通信。通常情况下，计算机作为主设备，显示器作为从设备。

EDID 读取: 计算机在启动时通过 DDC 读取显示器的 EDID，以确定最佳的分辨率和刷新率等设置。

命令发送: 计算机可以通过 DDC/CI 向显示器发送各种控制命令，比如：

调整亮度和对比度
切换输入信号源（如 HDMI、DisplayPort 等）
查询显示器当前的状态和设置

DDC/CI 的应用
显示器控制: DDC/CI 允许用户通过软件来控制显示器的许多设置，例如调节亮度、对比度和色温。许多监视器和显示器厂商都提供支持 DDC/CI 的软件工具来实现这些功能。

自动化脚本: 一些高级用户和系统管理员可以利用 DDC/CI 编写自动化脚本，以便远程管理和控制多个显示器的设置。

多显示器支持: 在多显示器环境中，DDC/CI 使得通过计算机系统统一管理多个显示器的设置成为可能。

如何使用 DDC/CI
软件工具
有几种工具可以帮助用户利用 DDC/CI 控制显示器：

DDC/CI 控制工具: 许多开源和商业软件，如 Monitorian （Windows 上的应用程序），可以通过 DDC/CI 来调整监视器的亮度和其他设置。

命令行工具: 例如 ddcutil 在 Linux 平台上，可以用来通过命令行与 DDC/CI 兼容的显示器进行交互。

注意事项
显示器支持: 并非所有显示器都支持 DDC/CI，因此确保你的显示器具有此功能。

驱动问题: 某些情况下，操作系统或显卡驱动程序可能需要支持 DDC/CI，以确保正常工作。

使用WMI调节显示器亮度

直接上代码吧，代码其实都是差不多的，主要在于你执行怎样的WQL操作，做什么样的操作。其余步骤都是差不多的。
头文件

#pragma once

#include 
#include "ui_QtTestPro.h"

class QtTestPro : public QMainWindow
{
    Q_OBJECT

public:
    QtTestPro(QWidget *parent = Q_NULLPTR);

    
    int Init();

    int GetBrightness();
	void PrintError(HRESULT hres);

    int SetBrightness(int brightness);

    void Cleanup();

    ~QtTestPro();


private slots:
    void on_btnUp_clicked();
    void on_btnDown_clicked();

private:
    Ui::QtTestProClass ui;
};

cpp文件

#include "QtTestPro.h"

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include

#pragma comment(lib, "wbemuuid.lib")
#pragma comment(lib, "comsuppw.lib")

using namespace std;

// wmi namespace
IWbemLocator* wmiLocator = NULL;
IWbemServices* wmiNamespace = 0;
BSTR wmiPath = SysAllocString(L"root\\wmi");
HRESULT hr = S_OK;

// brightnessAdjustmentClass
IWbemClassObject* brightnessAdjustmentClass = NULL;
IWbemClassObject* brightnessAdjustmentClassInstant = NULL;
IWbemClassObject* brightnessAdjustmentClassObject = NULL;
IWbemClassObject* brightnessAdjustmentMethodInstant = NULL;
IEnumWbemClassObject* brightnessAdjustmentClassEnum = NULL;

BSTR brightnessAdjustmentClassPath = SysAllocString(L"WmiMonitorBrightnessMethods");
BSTR brightnessAdjustmentMethodName = SysAllocString(L"WmiSetBrightness");
BSTR brightnessAdjustmentMethodArgName1 = SysAllocString(L"Timeout");
BSTR brightnessAdjustmentMethodArgName2 = SysAllocString(L"Brightness");
BSTR brightnessAdjustmentClassQuery = SysAllocString(L"Select * from WmiMonitorBrightnessMethods");


// brightnessClass
IEnumWbemClassObject* brightnessClassEnum = NULL;
//IWbemClassObject *brightnessClass = NULL;
IWbemClassObject* brightnessClassObject = NULL;

BSTR brightnessClassPath = SysAllocString(L"WmiMonitorBrightness");
BSTR brightnessVariableName = SysAllocString(L"CurrentBrightness");
BSTR brightnessQuery = SysAllocString(L"Select * from WmiMonitorBrightness");



QtTestPro::QtTestPro(QWidget* parent)
	: QMainWindow(parent)
{
	ui.setupUi(this);
	connect(ui.btnUp, &QPushButton::clicked, this, &QtTestPro::on_btnUp_clicked);
	connect(ui.btnDown, &QPushButton::clicked, this, &QtTestPro::on_btnDown_clicked);
	// 全局唯一
	//auto m = CreateMutexA(NULL, TRUE, "{CAF16FA1-1E0C-419B-9D45-99B5719ED318}");

	//if (ERROR_ALREADY_EXISTS == GetLastError())
	//	return;

	int r = Init();
	if (r != 0)
		return;

}

QtTestPro::~QtTestPro() {
	// 清理
	//UnregisterHotKey(hwnd, hotKeyId1);
	//UnregisterHotKey(hwnd, hotKeyId2);
	//GlobalDeleteAtom(hotKeyId1);
	//GlobalDeleteAtom(hotKeyId2);
	//Cleanup();
}

//
int QtTestPro::Init()
{

	// Initialize COM and connect up to CIMOM  
	hr = CoInitialize(0);
	if (FAILED(hr))
		return -1;
	hr = CoInitializeSecurity(NULL, -1, NULL, NULL, RPC_C_AUTHN_LEVEL_DEFAULT, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE, NULL);
	if (FAILED(hr))
		return -1;
	hr = CoCreateInstance(CLSID_WbemLocator, 0, CLSCTX_INPROC_SERVER, IID_IWbemLocator, (LPVOID*)&wmiLocator);
	if (FAILED(hr))
		return -1;
	hr = wmiLocator->ConnectServer(_bstr_t(L"ROOT\\WMI"), NULL, NULL, NULL, 0, NULL, NULL, &wmiNamespace);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	hr = CoSetProxyBlanket(wmiNamespace, RPC_C_AUTHN_WINNT, RPC_C_AUTHZ_NONE, NULL, RPC_C_AUTHN_LEVEL_CALL, RPC_C_IMP_LEVEL_IMPERSONATE, NULL, EOAC_NONE);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	//_bstr_t(L"ROOT\\CIMV2");
	// query variable enum
	hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), _bstr_t(L"Select * from WmiMonitorBrightnessMethods"), WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessAdjustmentClassEnum);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	/*hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), brightnessQuery, WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessClassEnum);
	if (hr != WBEM_S_NO_ERROR)
		return -1;*/


		// get class obj
	ULONG ret;
	hr = brightnessAdjustmentClassEnum->Next(WBEM_INFINITE, 1, &brightnessAdjustmentClassObject, &ret);
	if (hr != WBEM_S_NO_ERROR)
	{
		qDebug() << "Failed to retrieve the next object. Error code = 0x"
			<< hex << hr << dec << endl;
		return -1;
	}
		

	hr = wmiNamespace->GetObject(brightnessAdjustmentClassPath, 0, NULL, &brightnessAdjustmentClass, NULL);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	// get brightness adjust method instant
	hr = brightnessAdjustmentClass->GetMethod(brightnessAdjustmentMethodName, 0, &brightnessAdjustmentClassInstant, NULL);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	hr = brightnessAdjustmentClassInstant->SpawnInstance(0, &brightnessAdjustmentMethodInstant);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	return 0;


		//HRESULT hres;

		 Step 1: --------------------------------------------------
		 Initialize COM. ------------------------------------------

		hres = CoInitializeEx(0, COINIT_MULTITHREADED);
		//hres = CoInitialize(0);
		//if (FAILED(hres))
		//{
		//	PrintError(hres);
		//	qDebug() << "Failed to initialize COM library. Error code = 0x"
		//		<< hex << hres << endl;
		//	return 1;                  // Program has failed.
		//}

		 Step 2: --------------------------------------------------
		 Set general COM security levels --------------------------

		//hres = CoInitializeSecurity(
		//	NULL,
		//	-1,                          // COM authentication
		//	NULL,                        // Authentication services
		//	NULL,                        // Reserved
		//	RPC_C_AUTHN_LEVEL_DEFAULT,   // Default authentication
		//	RPC_C_IMP_LEVEL_IMPERSONATE, // Default Impersonation
		//	NULL,                        // Authentication info
		//	EOAC_NONE,                   // Additional capabilities
		//	NULL                         // Reserved
		//	);


		//if (FAILED(hres))
		//{
		//	cout << "Failed to initialize security. Error code = 0x"
		//		<< hex << hres << endl;
		//	CoUninitialize();
		//	return 1;                    // Program has failed.
		//}

		 Step 3: ---------------------------------------------------
		 Obtain the initial locator to WMI -------------------------

		//IWbemLocator *pLoc = NULL;

		//hres = CoCreateInstance(
		//	CLSID_WbemLocator,
		//	0,
		//	CLSCTX_INPROC_SERVER,
		//	IID_IWbemLocator, (LPVOID *)&pLoc);

		//if (FAILED(hres))
		//{
		//	cout << "Failed to create IWbemLocator object."
		//		<< " Err code = 0x"
		//		<< hex << hres << endl;
		//	CoUninitialize();
		//	return 1;                 // Program has failed.
		//}

		 Step 4: -----------------------------------------------------
		 Connect to WMI through the IWbemLocator::ConnectServer method

		//IWbemServices *pSvc = NULL;

		 Connect to the root\cimv2 namespace with
		 the current user and obtain pointer pSvc
		 to make IWbemServices calls.
		//hres = pLoc->ConnectServer(
		//	_bstr_t(L"ROOT\\CIMV2"), // Object path of WMI namespace
		//	NULL,                    // User name. NULL = current user
		//	NULL,                    // User password. NULL = current
		//	0,                       // Locale. NULL indicates current
		//	NULL,                    // Security flags.
		//	0,                       // Authority (for example, Kerberos)
		//	0,                       // Context object
		//	&pSvc                    // pointer to IWbemServices proxy
		//	);

		//if (FAILED(hres))
		//{
		//	cout << "Could not connect. Error code = 0x"
		//		<< hex << hres << endl;
		//	pLoc->Release();
		//	CoUninitialize();
		//	return 1;                // Program has failed.
		//}

		//cout << "Connected to ROOT\\CIMV2 WMI namespace" << endl;


		 Step 5: --------------------------------------------------
		 Set security levels on the proxy -------------------------

		//hres = CoSetProxyBlanket(
		//	pSvc,                        // Indicates the proxy to set
		//	RPC_C_AUTHN_WINNT,           // RPC_C_AUTHN_xxx
		//	RPC_C_AUTHZ_NONE,            // RPC_C_AUTHZ_xxx
		//	NULL,                        // Server principal name
		//	RPC_C_AUTHN_LEVEL_CALL,      // RPC_C_AUTHN_LEVEL_xxx
		//	RPC_C_IMP_LEVEL_IMPERSONATE, // RPC_C_IMP_LEVEL_xxx
		//	NULL,                        // client identity
		//	EOAC_NONE                    // proxy capabilities
		//	);

		//if (FAILED(hres))
		//{
		//	cout << "Could not set proxy blanket. Error code = 0x"
		//		<< hex << hres << endl;
		//	pSvc->Release();
		//	pLoc->Release();
		//	CoUninitialize();
		//	return 1;               // Program has failed.
		//}

		 Step 6: --------------------------------------------------
		 Use the IWbemServices pointer to make requests of WMI ----

		 For example, get the name of the operating system
		//IEnumWbemClassObject* pEnumerator = NULL;
		//hres = pSvc->ExecQuery(
		//	bstr_t("WQL"),
		//	bstr_t("SELECT * FROM Win32_DesktopMonitor"),//L"Select * from WmiMonitorBrightnessMethods  "SELECT * FROM Win32_OperatingSystem" "SELECT * FROM Win32_DesktopMonitor"
		//	WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY,
		//	NULL,
		//	&pEnumerator);

		//if (FAILED(hres))
		//{
		//	cout << "Query for operating system name failed."
		//		<< " Error code = 0x"
		//		<< hex << hres << endl;
		//	pSvc->Release();
		//	pLoc->Release();
		//	CoUninitialize();
		//	return 1;               // Program has failed.
		//}

		 Step 7: -------------------------------------------------
		 Get the data from the query in step 6 -------------------

		//IWbemClassObject *pclsObj = NULL;
		//ULONG uReturn = 0;

		//while (pEnumerator)
		//{
		//	HRESULT hr = pEnumerator->Next(WBEM_INFINITE, 1,
		//		&pclsObj, &uReturn);

		//	if (0 == uReturn)
		//	{
		//		break;
		//	}

		//	VARIANT vtProp;

		//	VariantInit(&vtProp);
		//	// Get the value of the Name property
		//	hr = pclsObj->Get(L"Name", 0, &vtProp, 0, 0);
		//	qDebug() << " OS Name : " << vtProp.bstrVal << endl;
		//	VariantClear(&vtProp);

		//	pclsObj->Release();
		//}

		 Cleanup
		 ========

		//pSvc->Release();
		//pLoc->Release();
		//pEnumerator->Release();
		//CoUninitialize();

		//return 0;   // Program successfully completed.

	
}


void QtTestPro::PrintError(HRESULT hres)
{
	LPVOID lpMsgBuf;
	FormatMessage(
		FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
		NULL,
		hres,
		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
		(LPWSTR)&lpMsgBuf,
		0, NULL);

	qDebug()<< L"Error: " << (LPWSTR)lpMsgBuf << endl;
	LocalFree(lpMsgBuf);
}

int QtTestPro::GetBrightness()
{
	// 每次都需要查询
	if (brightnessClassEnum) brightnessClassEnum->Release();
	if (brightnessClassObject) brightnessClassObject->Release();

	HRESULT hr = wmiNamespace->ExecQuery(_bstr_t(L"WQL"), brightnessQuery, WBEM_FLAG_FORWARD_ONLY | WBEM_FLAG_RETURN_IMMEDIATELY, NULL, &brightnessClassEnum);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	DWORD ret;
	hr = brightnessClassEnum->Next(WBEM_INFINITE, 1, &brightnessClassObject, &ret);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	// 获得亮度值
	VARIANT brightnessValue;
	VariantInit(&brightnessValue);
	hr = brightnessClassObject->Get(brightnessVariableName, 0, &brightnessValue, 0, 0);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	ui.label->setText(QString::number(brightnessValue.uintVal));
	return brightnessValue.uintVal;
}

int QtTestPro::SetBrightness(int brightness)
{
	// 亮度范围是 [0, 100]
	brightness = min(max(brightness, 0), 100);
	// write brightness adjust params
	VARIANT var;
	VariantInit(&var);
	V_VT(&var) = VT_BSTR;

	// write timeout param
	V_BSTR(&var) = SysAllocString(L"0");
	hr = brightnessAdjustmentMethodInstant->Put(brightnessAdjustmentMethodArgName1, 0, &var, CIM_UINT32);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	// write brightness param
	V_BSTR(&var) = SysAllocString(to_wstring(brightness).c_str());
	hr = brightnessAdjustmentMethodInstant->Put(brightnessAdjustmentMethodArgName2, 0, &var, CIM_UINT8);
	VariantClear(&var);
	if (hr != WBEM_S_NO_ERROR)
		return -1;

	// 获取 method instant path 和 execute
	VARIANT pathVariable;
	VariantInit(&pathVariable);
	hr = brightnessAdjustmentClassObject->Get(_bstr_t(L"__PATH"), 0, &pathVariable, NULL, NULL);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	hr = wmiNamespace->ExecMethod(pathVariable.bstrVal, brightnessAdjustmentMethodName, 0, NULL, brightnessAdjustmentMethodInstant, NULL, NULL);
	VariantClear(&pathVariable);
	if (hr != WBEM_S_NO_ERROR)
		return -1;
	return 0;
}

void QtTestPro::Cleanup()
{
	// 清理
	SysFreeString(wmiPath);
	SysFreeString(brightnessAdjustmentClassPath);
	SysFreeString(brightnessAdjustmentMethodName);
	SysFreeString(brightnessAdjustmentMethodArgName1);
	SysFreeString(brightnessAdjustmentMethodArgName2);
	SysFreeString(brightnessAdjustmentClassQuery);

	SysFreeString(brightnessClassPath);
	SysFreeString(brightnessVariableName);
	SysFreeString(brightnessQuery);

	brightnessAdjustmentClass->Release();
	brightnessAdjustmentMethodInstant->Release();
	brightnessAdjustmentClassInstant->Release();
	brightnessAdjustmentClassObject->Release();
	brightnessAdjustmentClassEnum->Release();

	//if (brightnessClass) brightnessClass->Release();
	brightnessClassObject->Release();
	brightnessClassEnum->Release();

	wmiNamespace->Release();
	wmiLocator->Release();

	CoUninitialize();
}


// 亮度进阶值
void QtTestPro::on_btnUp_clicked() {
	GetBrightness();
	SetBrightness(ui.lineEdit->text().toInt());
}

void QtTestPro::on_btnDown_clicked() {
	GetBrightness();
	SetBrightness(ui.lineEdit->text().toInt());
}